1. Field of the Invention
This invention relates to a semiconductor device composed of active elements, such as MISFETs, formed on a bulk Si substrate, an SiGe substrate, or an SOI substrate, and more particularly to a semiconductor device which has a shared contact that connects a source or drain region to a gate electrode by means of a contact.
2. Description of the Related Art
In a semiconductor device, such as a static random access memory (SRAM), formed on a semiconductor substrate, a configuration which uses a shared contact that connects a source or drain region to a gate electrode by means of a contact has recently been proposed (for example, Jpn. Pat. Appln. KOKAI Publication No. 2005-158898 or The 2003 Symposium on VLSI Technology Digest of Technical Papers, pp. 13-14).
This type of shared contact has a larger hole diameter than an ordinary contact hole because the source or drain region and the gate electrode have to be connected to each other. A shared contact with a larger hole diameter has a higher etching rate. Therefore, when a shared contact and an ordinary contact are processed at the same time, the insulating film (sidewall spacer) on the sidewall of the gate electrode is liable to penetrate. If the sidewall spacer has penetrated, the shared contact comes into contact with the extension of the source/drain region. Since the extension is very thin, if the shared contact penetrates the extension, this causes a junction leak.
To avoid this problem, a method of extending the gate electrode onto the element isolation insulating film and contacting the extended part to the source/drain region has been proposed (e.g., the 2006 IEDM Technical Digest, pp. 685-688). With this method, however, since the contact area of the shared contact becomes smaller, this causes the following problems: the resistance increases and securing the contact area prevents the miniaturization of the elements.